Tja får man tro Wikipedia så beror iallafall smällen när man använder en oxpiska på att änden når överljudsfart.
"Bullwhip
The cracking sound a bullwhip makes when properly wielded is, in fact, a sonic boom. The end of the whip, known as the "cracker", moves faster than the speed of sound, thus resulting in the sonic boom [1]. The whip was the first human invention to break the sound barrier.
A bullwhip tapers down from the handle section to the cracker. The cracker has much less mass than the handle section. When the whip is sharply swung, the energy is transferred down the length of the tapering whip. In accordance with the formula for kinetic energy , the velocity of the whip increases with the decrease in mass, which is how the whip reaches the speed of sound and causes a sonic boom."
(källa:
http://en.wikipedia.org/wiki/Sonic_boom)
Principen verkar bygga på att allt eftersom piskan smalnar av ( eller då kanske handduken) så får man en lägre massa, och för att energin i vågen skall vara konstant måste då hastigheten stiga.
/Hast